How to use a pointer multimeter to measure 400 microfarad capacitance?
Electrolytic capacitors used for filtering make up the majority of large-capacity capacitors over a few hundred microfarads. This type of capacitance typically has a substantial inaccuracy and a small amount of leakage. We need a capacitor with a large enough capacity and less leakage. The procedure and safety considerations for measuring capacitance with a pointer multimeter are described below:
First, discharge the capacitor pins by short-circuiting them with a metal object. The major goal of doing this is to prevent risk and minimize measurement errors because some charged capacitors are dangerous when discharged, which could harm humans in addition to damaging the multimeter. It still affects the measurement results even if there is only a tiny quantity of charge that cannot be felt by the human body.
It is possible to measure the discharged capacitor with certainty. Choosing the watch's gear is the second measurement stage. According to the gear selection theory, the middle of the dial is where the pointer can swing the furthest during a measurement. It is typically reasonable to select Rx10 for the capacitance of 400F when measured with MF47.
The capacitor will produce a charging current when it is connected to DC, and the larger the capacitance, the greater the current. It is equal to charging the capacitance using the meter's battery to measure capacitance using the file of a pointer multimeter. The pointer swing increases as the capacity does.
But 400°F has how much of a swing? Finding a new capacitor with a comparable capacity for comparison is necessary in this case. As a benchmark, we can choose a capacitor with a capacity of 470 F. While there may be minor variations among watch models, comparisons can be made as long as the pointer can swing to the centre. This theory states that some multimeters even mark the capacitance scale so you may take a quick measurement.
Additionally, it should be remembered that electrolytic capacitors have polarity, so measuring leakage current in the positive or reverse direction would result in different results. There is a minor leakage while connecting the red test lead to the capacitor's negative electrode, and a greater leakage when doing the opposite. The leakage decreases as the cursor swings back toward its starting location. You can also select the Rx1K file, which can be inspected in more detail, if you're just looking to measure the leakage. It should not be less than 1M when the red test lead is attached to the negative pole. The smaller the leakage (greater the resistance), the higher the tolerate voltage.
In addition, the capacitor must be discharged every time it is measured, otherwise the accuracy will be seriously affected.
Set the multimeter to 100Ω (resistance), short the two needles and adjust to zero. Connect the two needles to the two legs of the capacitor respectively. If the black needle is on the positive pole of the capacitor and the red needle is on the negative pole of the capacitor, this is called a forward charging measurement; otherwise, it is a reverse measurement. The swing of the hands of the forward measurement is very large, close to zero; the swing of the hands of the reverse measurement is relatively small. The method of measuring the capacitance is good or bad, no matter the forward measurement or the reverse measurement, the watch hand swings a lot and almost reaches the zero position, and then slowly swings back until it is close to infinity, indicating that the capacitance is good. If the hands of the watch directly reach the zero position without returning, it means that the capacitor has been broken down and damaged. If the watch hand hits any position in the middle and does not return, it means that the capacitor has serious leakage and cannot be used. If the hands of the watch do not move, it means that the capacitor has no capacity and cannot be used. The above is the method of measuring the quality of capacitance, and the measurement of other capacities is similar.
If the pointer needs to use a meter to measure the large capacitor, it can only simply judge whether the capacitor is short-circuited, whether the capacity is invalid, and the capacity reduction cannot be measured. The test method is to adjust the meter gear to the R resistance gear 1K position, short-circuit and discharge the positive and negative electrodes of the capacitor first, connect the black pen to the capacitor negative, and the red pen to the capacitor positive, the pointer of the normal watch will turn forward and close to the short circuit, and then the pointer will indicate the resistance It will gradually become larger, and finally close to infinity, so that the capacitor is basically fine and can be used. If the test shows that the pointer resistance is very low and does not move, it means that the capacitor is short-circuited internally. If the pointer does not respond, it means that the capacitor has failed.
